pass the active_tab directly to the template, to avoid copying app_conf
pass the active_tab directly to the template, to avoid copying app_conf

now that RAPIDSMS_APPS is being passed around persistantly, we can't
make arbitrary changes to it (in this case, adding 'active'=True to
the active tab) without copying it.

rapidsms/rapidsms-legacy,rapidsms/rapidsms-legacy,rapidsms/rapidsms-legacy